Folding machines

ABSTRACT

A machine folds a sheet by inserting a sheet in the bight between a pair of folder rollers, which may be varied in their separation to accomodate sheets having different folding characteristics. The sheet to be folded is first located in a preinserting position, lying in a plane which spans the gap between the folder rollers, and insertion is made by an inserter blade which strikes the sheet at its medial area and drives it into the roller bight. To condition the sheet for an accurate fold, a shuttle supports the sheet spanning the aforesaid gap until the time just prior to the inserter blade striking the sheet. The sheet may be tensioned or pulled taut in its pre-inserting position.

United States Patent 1 McCain et al.

[ 4] FOLDING MACHINES [7 51 Inventors: William B. McCain, I-linsdale;James I". Cosgrove, Western Springs; Edward J. Zagorski, Chicago, all ofI11.

[73] Assignee: McCain Manufacturing Corp.,

Chicago, Ill.

[22] Filed: Oct. 7, 1970 [21] Appl. No.: 78,663

[52] US. Cl. 270/80 [51] Int. Cl. B6511 45/04 [58] Field of Search270/67, 80-85; 271/45 [56] References Cited UNITED STATES PATENTS1,071,755 9/1913 King 270/82 1,128,537 2/1915 Sigafoos 271/45 3,132,7375/1964 Moon et al. 271/45 486,558 11/1892 Crowell 270/67 [111 3,749,394[451 July 31, 1973 7/1950 Anderson 270/80 3/1949 Malott 270/ 80 PrimaryExaminer-Robert W. Michell Assistant Examiner-A. Heinz Attorney--Kinzer& Dom

[5 7] ABSTRACT A machine folds a sheet by inserting a sheet in the bightbetween a pair of folder rollers, which may be varied in theirseparation to accomodate sheets having different foldingcharacteristics.

1 Claim, 13 Drawing Figures -I- FLAT sneer (stoma-was) m Pas-meantimePosmou.

Mao

lusanrso Susi? 55mg noaoeo Y \jfi a 1 III! 24 FOLDED sneer PAIENIED 3 13.749.394

sum 3 0F 6 a r a e O C 5 n h m w IL llll ll F 2 n B 2 I m a m a p H. K\.l m. m m H n n 5 A m. H1 w I (A H F (\..-n m o n u m w: I l u inn 7 6 2B x: H v u u 5 H OIL! nH W "v c H a WM U 7 HI H rm. Lu w -\\H! r l 10 .O2 w W srov; Edward J. zasorskl 785 James F. Cos

,IDm m4 Ziokmi' .fifiornegs PATENIED 1 3.749.394

sum 5 0F 6 Inventors wi lliam B. M Cain,

James F. Cosgrove Edward J.Zagors ki.

FOLDING MACHINES This invention relates to a machine for imparting amedial fold to a sheet orsignature.

Bookssuch as magazines and the like are composed of signatures which inthe most simple form is a folded sheet presenting four pages of text orother printed matter. The signatures are assembled in individual hoppersor pockets and are fed therefrom in the proper sequence onto a conveyorto compose a book. Thereafter the assembled signatures are joined bystitching or glumg.

The signatures may be gathered on a saddle conveyor in which event thesignatures are dropped one atop another so that the folded backbones arenested. The nested signatures may be joined by staples driven throughthe assembled backbones, the staples piercing the signatures colineallywith the fold lines.

In another form of signature gathering machine, a flat or side gatherer,the signatures are collected one atop another in a flat state and arejoined by staples that pierce the margin adjacent the fold line, forminga book with a so-called square back in contradistinction to a bookproduced on a saddle conveyor where the back of the book is V-shaped.

In any event the machine of the present invention is converned withfolding a sheet, and while one mode of utility is in terms of producingsignatures it will be appreciated that the invention is not sorestricted.

The sheets to be folded may in fact be a book cover, or it may be aninterior signature. Usually a book cover is of relatively hard papercompared to the softer paper which is usually the form of an interiorsignature. The

present machine-is constructed to take into account the differentfolding characteristics of a hard sheet and a soft sheet. Thus ahardcover, if folded on a bend which is too sharp, may break or crack, andtherefore one of the objects of the present invention is to avoid thispossibility by so constructing the machine as to enable a soft or easyfold to be imparted to ahard sheet whiledisregarding this possibility inthe instance of soft sheets. I

The present machine is capable of handling thick signatures which may befed to the machine, already in a partially folded state. A signature ofthis character is of 7 course much thicker than a single sheet tobefolded, and another object of the inventionis to enable apair offolder rollers to be adjusted to'vary the width of the bight or throatwhich imparts the fold to the signature or sheet- As suggested above,folding in the presentmachine is accomplished by apair of folderrollers. The sheet to be folded is forced to the bight of the folderrollers by an inserter blade which concurrently starts thelfold. Priorto being so inserted, the sheet to be folded is located in apre-inserting position, lying in a plane which spans the gap between thefolder rollers. The sheet may tend to sag, resulting in an inaccuratefold, and one of the more important objects of the present invention isto temporarily support the sheet in its pre-inserting position by areciprocal shuttle, the shuttle being displaced from its supportingattitude just prior to the time the inserter blade strikes the sheet tostart the'fold. A related object of the present invention is to stretchor render the sheet taut in its preinserting position, since to do socontributes to the attainment of an accurate fold.

Other and further objects of the present invention will be apparent fromthe following description and claims and are illustrated in theaccompanying drawing which, by way of illustration, shows a preferredembodiment of the present invention and the principles thereof and whatis now considered to be the best mode contemplated for applying theseprinciples. Other embodiments of the invention embodying the same orequivalent principles may be made as desired by those skilled in'the artwithout departing from the present invention.

In the drawing: FIG. 1 is a perspective view of a machine constructed inaccordance with the present invention;

FIG. 2 is a fragmentary perspective view of the front of the machine,enlarged as compared to FIG; 1;

FIG. 3 is a plan view of a portion of the machine; FIG. 4 is a plan viewof apparatus associated with a sheet stop and a sheet tensioner;

FIG 5 is an elevational view on the line 5+5 of FIG. 3;

FIG. 6 is a sectional view on the line 6-6 of FIG. 3;

FIG. 7 is a fragmentary sectional view of the machine;

FIG. 8 is a detail sectional view of parts associated with the shuttleand being taken on the line 8-8 of FIG. 9;

FIG. 9 is a detail elevation of the, shuttle; FIG. 10 is an endelevation of the shuttle structure;

FIG. 11 isa sectional view on the line 11-ll of FIG. l0; Y FIG. 12 is adetail sectional view on the'line 12-12 of FIG. 9; and

FIG. 13 is a sectional view on an enlarged scale showingthe constructionat the folding station.

The folding machine 20, FIG. 1, receives an unfolded sheet, or a partlyfolded sheet or signature (for further folding) movingalong the'in-feedpath as shown. The sheet is transferred bytape feeders, ashereinafter-described, to the folding station. After the sheet isfolded, it is delivered for further processing, as for instance deliveryto a signature gatherer.

Referring to FIG. 7, in-feed rollers as 22 and 22A re-' ceive the sheetto be folded andadvance it along a guide and support plate 23 to opposedin-fee'd tapes 24 and 26, arranged in pairs (see FIG. 3) or even fours.which advance the sheet forwardly along the plate 23 in the direction ofthe folding station. The rear turns of the tapes 24 and 26 are trainedaround rear pulleys or rollers 28 and 30, FIG. '7. The upper tapes '26are trained around forward rollers 32, and are tensioned by'intermediateidler rollers 34 carried on adjustable arms 35, FIG. 3.

The lower in-feed tapes 24 are presented to grooves in folder roller (55hereafter) and then extend forward to (idler) pulleys or rollers 36;from thence in a return direction to tensioner rollers 37 supported onan adjusting arm as 37A, thence upwardly about idlers 38 and finally tothe rear rollers 28.

A set of forward tensioning rollers 40, FIG. 7 is also provided for theupper in-feed tapes 26. These rollers are supported for rotation by across shaft 41, FIG. 3, supported in turn by brackets 42 secured'byscrews 44, FIG. 7, at the ends of another cross shaft 44A, FIGS. 2 and3, mounted in slots 45 formed in downwardlyand forwardly extending arms46. The arms 46 are bifurcated, FIG. 7, and are tightened on a supportshaft 48 by screws 50.Resultantly, by loosening screws 44 and 50, FIG.7, the supports 42 may be extended or retracted to displace the rollers40, thereby to vary the location of the forward bight between thein-feed tapes 24 and 26. Thisadjustment, for sheet size, assures thatthe sheet will be moved accurately against the sheet stop, hereinafterdescribed, without significant buckling.

A driven shaft 54, FIG. 7, supports a plurality of rear folder rollers55, the folder roller 55 being opposed to a like number of forwardfolder roller 56 carried by a driven shaft 57.

The rollers or tape pulleys thus far described are driven by chains andgears in a manner which is apparent from FIG. 7. Thus, chain 61 drivesgears 62 and 63 for the folder roller shafts 54 and 55, and at the sametime the tapes 24 are driven as an incident.

Drive shaft 54 carries a gear 66 about which a chain 65 is trained.Chain 65 extends to a gear 68 which drives the shaft 69, FIG. 7, for thein-feed rollers 22.

Another gear (not numbered) on this same shaft drives a chain 70 trainedabout a gear train 71-72-73 for driving shaft 74 which carries eachdrive pulley as 30 for the upper in-feed tapes 26.

Advantageously, shaft 74 is supported by a pair of arms 75, FIG. 7,pivoted about shaft 76 which carries gear 71, being tensioned clockwiseby a spring 77, which allows the assembly to yield to any in-feed jam oroverload. The shaft for in-feed rollers 22A is supported in like manneras will be apparent from FIG. 7 by means including arms as 228, pivotedon shaft 76 and tensioned by a spring 22C to engage rollers 22A withrollers 22. Rollers 22A are carried on a shaft 22D driven by a gear 226meshed with gear 72.

The folder rollers, FIGS. 7 and 13, are separated at the nearest pointby a narrow throat or bight B and at their widest point thereabove by agap G. The sheet to be folded, in-fed by the tapes to the foldingstation, spans the gap G so that the leading portion moves on to asupport plate 23A on the opposite side of the gap G. ln-feeding iscontinued by the tapes 24 and 26, until the'leading end of the sheet ispicked up by a pair of tapes 78, FIGS. 3 and 7, which present theleading edge of the in-fed sheet to a stop as hereinafter described.

The sheet to be folded spans the gap G in its preinserting position, andas will be described in detail below,.the medial portion of the sheet tobe folded is accurately located in centered position above the foldingbight B. The sheet is moved from this position into'the folding bight byan inserter blade 80 adjustably supported on the outer face of a crossplate 82 in turn supported by a pair of rocker arms 85. The lower edgeof the folding or inserter blade 80 is serrated at 8015, andadditionally is provided with a pair of needle-like projections of smalldiameter (not numbered) which actually pierce the sheet when it isstruck by the folding edge of the blade 80.

The arms 85, FIGS. 3 and 7, are pinned to the outer ends of a rock shaftextending between and supported by the side plates of the machine.Springs 91, FIGS. 1 and 2, are anchored at the lower end to a stud 92fixed to the side of the machine, and at the upper end each spring isanchored to a stud 93 on the related arm 85. Hence the springs 91 tendto rock the folder blade clockwise as viewed in FIGS. 1, 2, and 7, butsuch tendency is resisted and controlled by a pair of cams as 95, FIGS.2 and 3, carried at the outer ends of a cam between the tapes 24 and 98.

shaft 96 having a gear 96G which is turned by chain 61, FIG. 7, each cambearing on a cam follwer 97 on the outer side of the related foldersupport arm, FIG. 2.

It will be appreciated, of course, that the reciprocal stroke of thefolder blade 80, downward from its retracted position, FIG. 7, issufficient to move the sheet from its pre-inserting position into thefolder bight B. During this movement the fold is of course started,particularly as this is aided by the tensioning means to be describedbelow, and eventually the tapes 24 take over and assure movement of thepartially folded sheet into and through the bight. In this connection,and referring to FIG. 7, feed tapes 98 are trained around the forwardfolder rollers 56 and around rear tensioner rollers 99 and hencecooperate with the tapes 24 in accepting the sheet from the folder bladeand moving the sheet through the folding bight or nip B.

Another pair of tapes 100 are trained around the folder roller 56 andthe tensioner rollers 99, and these tapes are in contact with the tapes78 so as to drive the latter about their guide rollers 78A, 78B and 78C.

Rollers 99, for the feed tapes 98, are supported for vertical adjustmentso that the gap of separation between the tapes 24 and 98 may be variedfor a strong drive or an easy drive of the folded sheet to the point ofdelivery, FIG. 7. To this end, the rollers 99 are supported for rotationon a shaft 101 extended through vertically elongated slots 102 in theside plates of the machine, FIG. 7. Shaft 101 in turn is supported ateach end'in a block 1028, FIG. 2. Each block 1028 is pinned to the lowerend of an adjusting screw 103, extended freely through an opening in aguide ear 103E, fixed to the side plate of the machine. A spring 104 isfitted about the'shank of the screw 103 in the portion thereof betweenthe block 102B and the ear 103E soas to allow the rollers 99 to yield toany jam or overload. The end of the screw 103 above the ear 103Eisthreaded and provided with an adjusting and lock nut assembly 104A and1048 respectively, enabling the position of shaft 101 to be adjustedthereby .to vary the separation It was mentioned above thatadjustment ofthe tensioning roller 40 associated with the upper in-feed belt 26 inpart is concerned with properly advancing a sheet of predeterminedlength to a stop means. The stop means and the associated parts areshown in detail in FIGS. 4 to 6, and specifically the stop is in theformof a bar or blade 105, FIGS. 4 and 6, which, asshown in FIG. 7, isnormally in a stop position on the right-hand side of the folder rollers56.

The stop blade 105 is substantially L-shaped, FIG. 6, being providedwith an offset .107 juxtaposed on the upper edge of a support bar 108.The offset 107 is interposed between the support bar l08 and a pair ofthumb screws having bosses 112, FIG. 6, at the underside thereof adaptedto be tightened against the offset 107 to fix the stop blade in anadjusted position.

The offsets are provided with open-ended slots 112, FIG. 4, such that byloosening the screws the blade may be adjusted uniformly along itslength or tilted at an angle, if necessary, to afford the necessaryaccurate stop edge for the leading edge of the sheet moving across thegap G in the direction of the stop.

The support bar 108, outward of the stop blade 105, is provided withtapped openings 108A, FIG. 4, threadedly related to a pair of elongatedadjusting screws 1 15. The extremities of the support bar 108 areprovided with apertures 1088 which fit a pair of guide bars 116. Theends of the screws 115 and the ends of the guide rods 116 are supportedin cross supports 117 and 118.

Referring to FIG. 4 the ends 120 of the screws 115 are journalled in thesupport bar 118, and the opposite ends are rotatably supported in thecross support 117, having extensions outward of the support 117 providedwith gears 121 and 122 about which is trained flexible toothed belt 125.The screw 115 having gear 121 is provided with a knob 126, such that byturning the knob 126 both screws 115 may be turned to advance or retractthe support bar which carries the adjusting blade 105. As shown in FIG.2, the cross support 117, at its opposite ends, is fastened to the sideplates of the machine, 130.

Advantageously the leading and trailing margins of the sheet in itspre-inserting position are tensioned somewhat, or in any event are heldtaut to assure that the sheet is properly stretched across the gap G sothat the fold may be accurately made, and to this end a pair of springbiased rollers 132, FIG. 3, are superimposed on the tapes 78. Thus thesheet advancing across the gap under the direction of the in-feed tapes24 and 26 is forced between the rollers 132 and the opposed tapes 78thereunder which clamps opposite sides of the sheet at the leading end.

Referring to FIGS. 4 and 6, each roller 132 is rotatably supported on ahorizontal pin 133, and each pin 133 in turn'is carried on a support arm134. The support arm 134 in turn is carried by a support pin 135threadedly mounted in a bracket 136 fastened to the cross support 118.Each pin 135 had an adjusting knob 135K and a lock nut 135N. A torsionspring 138'is mounted on the pin 135 and is effective between arm 134and knob 135K to urge the related roller 132 by slight spring tensiondownward into contact with the tapes 78. Washers 139 are mounted on eachpin 135 between arm 134 and the bracket 136. By turning knob 135K in orout as the case may be, to vary the force of spring 138 on arm 134, theeffectiveness of the spring may be regulated, thereby determining theforced the rollers l32 bearing on the sheet. Y 1

It is appropriate-to note in connection with the advancement of thesheet across the gapG that a'plurality'.

of guide fingers 140, FIGS. 4 and 7, overlie the support plate 23Athereby constraining the sheet for straight forward movement toward thestop 105. In like manner, guide fingers 141, FIGS. 3 and 7, spacedslightly above the support plate 23, are arranged to constrain the sheetin the course of its movement across the gap G as hereinafter described.

Referring to FIGS3and 13, a tie bar 143, spans and is fastened to theside plates 130 and a pair of brackets 144' and fastened thereto inspaced relation as a convenient mode of presenting additional sheettensioners for the trailing portion of the sheet. To this end eachbracket 144 supports a hollow housing 145v provided with a verticallyoriented chamber 146 in which is disposed a compression spring 147applying pressure to a ball 148 normally bearing on the support plate23. The spring 147 is of such nature as to press the ball 148 lightlyagainst the plate 23 but not with a force of such order as to preventthe passage of the sheet therebetween, and when the trailing end of thesheet is therebetween it is clamped on opposite sides by the ball 48andplate 23. Nonetheless, when a sheet is finally against the stop blade105, both the rollers 132 and the balls 148 serve to tension the sheetsufficiently to in effect hold the sheet in a true horizontal plane atthe time the inserter blade is effective to force the sheet toward thebight of the folder rollers.

The folder roller 56, supported on theshaft 57, are arranged foradjustment toward and away from the opposed folder rollers 55. Thisenables the folding bight to be adjusted both for sheet thickness and tovary the folding pressure, inasmuch as a hard sheet ought not to befolded so forcefully as softer sheets.

To this end, and as shown in FIGS. 2 and 7, shaft 57, at each end, isrotatably supported by an arm 150,-and at its lower end arm 150 ispivotally supported on a pin 151, FIG. 7. The upper end of the arm 150is fastened to the bifurcated end of a link 152, and link 152 extendsthrough an aperture in an car 153 extending outwardly from the sideplate of the machine. The end of link 152 opposite the bifurcation isprovided with adjustable lock nuts 154. A compression spring'ISSsurrounds the portion of link 152 lying between ear 153 and thebifurcated end of the link. By loosening or tightening the lock nuts asthe case may be, link 152 may be varied, thereby shifting the supportarm as incidental to narrowing or widening the bight B. Spring 155imparts a degree of yieldability to the folder rollers 56.

In order to obviate the possibility that the leading portion of thesheet may sag into the bight B as" it crosses the gap G, a reciprocalsupport or shuttle is provided under and in accordance with the presentinvention to support the sheet during this transitional period.Referring to FIGS. 9 through 12 the preferred form of the supportincludes forwardly projecting fingers fastened to a shuttle 161. Thefingers 160 are relatively thin and are aligned with guide grooves inthe folder rollers 55 to reciprocate therein. Means are provided to movethe shuttleand the fingers 160 forwardly to an active position inaccordance with the need to provide temporary'support for the sheet,while withdrawing the fingers 160 to their retracted position at thetime when the folder blade commences its operative stroke.

The shuttle 161 is in the form ofa rectangular plate and the oppositeends thereof are associated with guide means which confine the shuttleto therequired reeipv rocal path. Thus associated pairs of guiderollersl62 are supported for rotation on journal pins l63 atthe ends ofthe. guide rails 165, and the guide rails 165 are secured in dependingrelation to the. underside to the guide plate 23 as shown in FIG. 12. Toassure smooth action and little friction, roller bearing races #167"areinterposed between'the rollers 162 and the journal pins The journalpins are eccentric stubs, depending from a head 168 seated snugly in arecess 168R forward in the cross support 161. By loosening a nutl69,'thread-' edly attached to the lower end of the eccentric stub 163,the head 168 may be turned, thereby tightening or loosening the fitbetween the guide roller 162 and the guide rail 165. y

In order that the shuttle may be reciprocated in-an accurately timedrelationship, shuttle control means-of a cam operated type are provided.To this end a pair'of shuttle support arms 170, FIG. 10, arefastened-to-a rock shaft supported by and extending between the sideplates of the machine as shown in FIG. 10, Theupper 1 ends-of the arms170 are bifurcated as shown in FIG. 11 and embrace rollers 173 supportedat the underside of the carrier or shuttle 161 as shown in FIG. 10. Thuswhen the rock shaft 171 is oscillated the shuttle support carrier 161travels in a horizontal path in a manner now to be explained.

Cam shaft 96, FIG. 11, carries a shuttle control cam 177 associated witha cam follower 178. The cam follower 178 is carried at the upper end ofan arm 179, and arm 179 is adjustably secured to the rock shaft 171.Shaft 171 is spring biased so that the follower 178 is normally heldagainst the cam 177, and referring to FIGS. 10 and 11 and arm 180 issecured to the rock shaft 171, depending therefrom. The lower end of arm180 is provided with a stud 181 on which the lower end of a spring 182is anchored, the upper end of the spring (not shown) being suitablyanchored so as to apply tension to arm 180.

As shown in FIG. 11 cam 177, which controls operation of the shuttle, iscarried on the cam shaft 96 and has two diametrically opposed lobes177L. When a cam lobe 177L is presented to the follower 178 the shuttlesupport arm 161 is reciprocated rearwardly to dispose the supportfingers 160 in their ineffective position. This would be at a time whenthe folder blade is undergoing its downward or operative stroke. Then asthe folder blade attains its upper or retracted position the dwell orlow part of cam 177 is presented to the follower 178, whereby the fingersupport shuttle commences its forward stroke as impelled by spring 182whereby. the fingers 160 move forwardly in the guide grooves providedtherefor in the folder rollers 55 at a time when the next sheet to befolded is traversing the wide gap G, and in fact the support fingers 160span the gap G before the leading edge of the next sheet to be foldedreaches the gap G. The support fingers 160 are withdrawin rearwardlyunder control of cam 177 in the course of the downward stroke of thefolder blade, and are completely withdrawn or retracted at the time thefolder blade engages the medial portion of the sheet incidental todriving it into the folding bight B.

It will be seen from the foregoing that under the present invention asheet is folded by a pair of folder rollers, provision being made foradjusting the dimension of the folding bight or nip between the rollersaccordingly as the sheet is of such nature as to require a soft foldor ahard fold. The sheet is delivered to the folder rollers by an inserterlocated above the gap between the rollers. The sheet to be folded,spanning the gap, is stretched to a taut state by tensioners acting asclamps on both the leading portion and the trailing portion. This stateof tension prevails when the inserter engages the sheet, andconsequently the sheet is in condition to have a sharp fold impartedthereto as the inserter drives the tensioned sheet into the foldingbight presented by the folder rollers.

The sheet to be folded is driven forwardly by endless feed bands ortapes, and these are adjustable with respect to an adjustable stop onthe far side of the folding bight so that the in-feed tapes and the stopmay be adjusted to comply with the prevailing circumstances so far asconcerns sheet length. As the sheet traverses the gap between the folderrollers, moving beneath the inserter means, temporary support is lentthereto by means of the support shuttle and its fingers.

Hence, while we have illustrated and described the preferred embodimentof our invention, it is to be understood that this is capable ofvariation and modification.

We claim:

1. A machine for folding sheets comprising a pair of opposed folderrollers supported for rotation in opposite directions on horizontal axesat a folding station and defining a narrow vertically oriented foldingbight between which a sheet is inserted for folding, means forin-feeding the sheet in its flat unfolded state along a feed path to apre-inserting position in a plane spanning the gap between the rollers,the sheet so fed passing a first one of the folder rollers and then thesecond one, an inserter blade spaced opposite the flat sheet in itspre-inserting position, means to impart an insertion stroke to theinserter blade during the extent of which the blade engages the sheet inits pre-inserting position to start a fold therein and concurrentlyinserts the partly folded sheet in the bight between the rollers whichare to complete the fold, means to return the inserter blade to itsstarting position following an insertion stroke, a stop in said feedpath located behind said second one of the rollers passed by the in-fedflat sheet, said stop being in position to engage the leading edge ofthe sheet to be folded and accurately locate the sheet relative to theinserter blade, a reciprocal-shuttle presenting a reciprocal sheetsupport in said feed path for bridging the gap between the folderrollers to lend temporary support to the in-fed sheet as it moves acrosssaid gap toward said stop, a fixed sheet support plate in advance of thefirst folder roller and on which the trailing part of the sheet isdisposed when the leading edge engages the stop, means located onopposite sides of the folding bight-to apply tension to the leading andtrailing portions of the sheet spanning the folding bight, saidlast-named means including additional sheet feed means located betweensaid stop and said second folder roller and gripping opposite sides ofthe sheet to feed the sheet toward said stop and said tensioning meansfurther including means pressing the trailing part of the sheet againstsaid sheet support plate with a predetermined amount of pressure whilesaid additional sheet feed means presents the leading edge of the sheetto said stop whereby said pressing means and said additional sheet feedmeans cooperate to stretch the sheet tautin its pre-inserting positionwhen itsleading edge is against the stop as aforesaid, means forwithdrawing the shuttle before the inserter blade engages the sheet tobe folded, said addition sheet feed means comprising a feed tape and anopposed roller engaging opposite sides of the sheet, and said pressingmeans comprising a spring biased member and means for regulating theeffect of the spring.

1. A machine for folding sheets comprising a pair of opposed folderrollers supported for rotation in opposite directions on horizontal axesat a folding station and defining a narrow vertically oriented foldingbight between which a sheet is inserted for folding, means forin-feeding the sheet in its flat unfolded state along a feed path to apre-inserting position in a plane spanning the gap between the rollers,the sheet so fed passing a first one of the folder rollers and then thesecond one, an inserter blade spaced opposite the flat sheet in itspreinserting position, means to impart an insertion stroke to theinserter blade during the extent of which the blade engages the sheet inits pre-inserting position to start a fold therein and concurrentlyinserts the partly folded sheet in the bight between the rollers whichare to complete the fold, means to return the inserter blade to itsstarting position following an insertion stroke, a stop in said feedpath located behind said second one of the rollers passed by the in-fedflat sheet, said stop being in position to engage the leading edge ofthe sheet to be folded and accurately locate the sheet relative to theinserter blade, a reciprocal shuttle presenting a reciprocal sheetsupport in said feed path for bridging the gap between the folderrollers to lend temporary support to the in-fed sheet as it moves acrosssaid gap toward said stop, a fixed sheet support plate in advance of thefirst folder roller and on which the trailing part of the sheet isdisposed when the leading edge engages the stop, means located onopposite sides of the folding bight to apply tension to the leading andtrailing portions of the sheet spanning the folding bight, saidlast-named means including additional sheet feed means located betweensaid stop and said second folder roller and gripping opposite sides ofthe sheet to feed the sheet toward said stop and said tensioning meansfurther including means pressing the trailing part of the sheet againstsaid sheet support plate with a pre-determined amount of pressure whilesaid additional sheet feed means presents the leading edge of the sheetto said stop whereby said pressing means and said additional sheet feedmeans cooperate to stretch the sheet taut in its pre-inserting posItionwhen its leading edge is against the stop as aforesaid, means forwithdrawing the shuttle before the inserter blade engages the sheet tobe folded, said addition sheet feed means comprising a feed tape and anopposed roller engaging opposite sides of the sheet, and said pressingmeans comprising a spring biased member and means for regulating theeffect of the spring.